1. Field of the Invention
The invention relates to a method of forming a trench, and in particular to a method of forming a trench by a silicon-containing mask.
2. Description of the Prior Art
Integrated circuits are manufactured as assemblies of various devices. In the further development of modern semiconductor technologies, trench structure semiconductor devices or components with a trench structure are also increasingly being used. For example, deep trench isolation structures are employed in conventional systems, and are commonly used in order to reduce the total device area and provide good isolation between elements. Furthermore, interconnections are often made by means of contact plugs. The contact plugs is formed through filling the trenches with a metal or other conductive material to connect the individual devices. Other example of trench structure semiconductor devices may include trench gates, or trench capacitors.
FIG. 1 to FIG. 2 are schematic diagrams showing a conventional method of forming a trench. As shown in FIG. 1, a substrate 10 is covered by a pad oxide 12 and a patterned silicon nitride mask 14. Please refer to FIG. 2, numerous trenches 16 are formed by taking the patterned silicon nitride mask 14 as a mask. However, because the etching rate between silicon nitride and silicon oxide are different, a recess 18 may be formed in the pad oxide 12, and the sidewall of the trenches 16 becomes uneven.